Heretofore, as a measuring cap for measuring and extracting a liquid contained in a squeezable bottle, there have been known the following three types:
(a) having an inner plug containing a measuring cup, the inner plug is attached to the bottle neck and the opening of the plug is closed by a screw cap (for example, Japanese Patent Publication Sho 63-44630 and Japanese Utility Model Publication Sho 63-35973),
(b) a step is formed to a bottle neck and an inner plug constituting the bottom of a measuring chamber is fit to the step to constitute a measuring cup by the bottle neck per se and a cap is screw coupled to the opening of the bottle (for example, Japanese Utility Model Laid-Open Sho 61-99568)
(c) a measuring chamber is constituted by fitting an inner plug to a cap main body, in which an over flow port of the inner plug connected with a supply pipe is opened or closed by a button and the pouring mouth of the measuring chamber is left open (for example, Japanese Patent Publication Sho 47-4790).
In both conventional types (a) and (b) described above, since the upper portion of the measuring chamber is entirely opened to form a pouring mouth, the pouring mouth is inevitably enlarged making discharge difficult and liquid draining poor tending to cause dripping. Further, in the said type (a), since the outer circumference of the measuring chamber is in three or two layers because of the overlap of the circumferential wall of the bottle neck, side wall of the measuring cap and the side wall of the cap and since it is situated to the inner side of the wall formed with threads, it is difficult to externally observe the state of the inner liquid discharged to the measuring chamber even if they are made of transparent material. Thus, if it is intended to extract a smaller volume than the constant volume, it is only possible to control the squeezing of the bottle by a hunch and a liquid of a volume less than the constant volume can not easily be extracted by measuring. Further, since the wall portions are overlapped, the material cost is increased by so much.
Further, the said type (b) has a drawback that the shape of the bottle neck is complicated and the capping step after charging the inner liquid needs two steps, i.e., a step of exactly fitting an inner plug having a disc constituting the bottom wall of the measuring chamber to a deep position of the bottle neck in a tightly sealed state and a step of screw-coupling the cap making it complicated thus reducing the efficiency extremely in the capping step. Further, if the measuring chamber is left open as in type (c), liquid remaining after use in the measuring chamber may coagulate or it may spill when the bottle falls over.
Further, since the bottom wall of the measuring chamber is flat in the conventional type, even if the inside of the measuring chamber can be observed visually from the outside, it is difficult to discharge a small volume of liquid under observation. Furthermore, in a case where the cap is adapted to be attached by screwing, it has a drawback that the cap has to be removed upon every use and also making it impossible to conduct one-touch operation.